1. Field of the invention
The present invention relates a method and apparatus for the simultaneous transmission of two separate data signals using the technique known as spectrum spreading by direct sequence or pseudo-noise.
2. Summary of the prior art
When discreet, confidential and jamming resistant transmission of data is required, it is known to make use of so-called wide-band spectrum spreading techniques. In the case of the direct sequence spreading technique, the useful signal to be transmitted modulates a spreading code in the form of a pseudo-random sequence of binary values, the rate of which is far higher than the band width of the useful signal. On reception, the coded signal received is correlated with a pseudo-random code generated by the receiver, the setting of which enables a synchronizing device to restore the initial useful signal. However, while this technique allows the transmission of any type of variable rate data, whether analog or numerical, it cannot provide for the simultaneous transfer of several data signals without resorting to complex multiplexing techniques and using only one pseudo-random code.